Electric current rectifying system



June 20, 1933. E. KOBEL 1,914,747

ELECTRIC CURRENT RECTIFYING SYSTEM Filed May 11, 1932 Patented June 20, 1933 ERNST KOBEL, OF ENNETBADEN, SWITZERLAND ELECTRIC CURRENT RECTIFYING SYSTEM Application filed May 11, 1932, Serial No. 610,571, and in Germany May 13, 1931.

This invention relates to improvements in electric current rectifying systems employing a rectifier of the metallic vapor arcing type and relates more particularly to such systems provided with means for discharging surges in the system through the rectifier;

' The transformer supplying alternating current to an electric current rectifier is a frequent source of high potential surges which must be discharged from the system and are preferably discharged through the rectifier. hen a rectifier of the metallic vapor arcing type is used, discharge of such surges is like- 1y to cause backfires whichmay seriously 9 damage the rectifying system. Such potential surges should be discharged by means other than the portions of the rectifier em" ployed in obtaining the rectifying action to avoid disturbance of the rectifying action and to avoid disturbances in the output circuits of the rectifier. Potential surges may be discharged by means of spark gaps formed by an electrode arranged within the rectifier casing and cooperating with such caslng providing the electrode is arranged within a zone within the rectifier of high vapor density and ready accessibility of metallic ions, or an auxiliary anode, may be associated with each main anode of a rectifier in such manner that the resistance to discharging of surges by wav of the auxiliary anodes is less than the resistance to such discharges by way of the main anodes. Such spark gaps or auxiliary anodes then readily break down and produces an are thus securing discharging of surges before such surges can discharge over the main anodes and cause backfires or short circuits within the rectifier or disturbances in the direct current output circuit of the recti- 4 fier.

Research has shown, however, that the operation and safety of auxiliary electrodes as sociated with the main anodes of an electric current rectifier of the metallic vaportype is r very materially improved if the auxiliary electrodes are arranged within the field of a continuous arc and have such are contacting thereon. Such improved operation appears to be due to the intensive ionization of the vapor adjacent the auxiliary or discharge electrodes which establishes a path of low resistance to the discharging of potential surges by way of such electrodes and causes operation of the discharge electrode path upon theoccurrence of any potential in the system greater than the normal operating potential. I

It is therefore among the objects of the present invention to provide means for dis charging potential surges in electric current rectifying systems employing an electric current rectifier of the metallic vapor arcing type in such manner as not to affect the main anodes employed in the rectifying action.

Another object of the invention is to provide such means for discharging potential surges in electric current rectifying systems of the metallic vapor arcing type as will cause the discharging of such surges before such conditions can arise as will cause disturbance of the rectifying action and before the occurrcnceof harmful disturbances in the direct current output circuit of the rectifier.

Another object of the invention is to provide an electric current rectifier, of the metal- 110 vapor arcing type, with auxiliary electrodes to form a path for more readily discharging potential surges in the rectifying system than by way of the main anodes of the rectifier.

Another object of the invention is to pro vide an electric current rectifier, of the metallic vapor arcing type, with auxiliary electrodes arranged within the field of a continuous arc and associated with the main anodes to form a path for more readily discharging potential surges in the rectifying system than such surges could be discharged by way of the main anodes of the rectifier.

Objects and advantages other than those 7 above set forthwill be apparent from the following description when read in connection with the accompanying drawing in which:

Fig. l is a schematic representation of one embodiment of the present invention in which an auxiliary anode supplied from a source of current other than therectificr supply trans former secondary winding or the direct current output circuit of the rectifier, is arranged to provide an are for establishing and maintaining a field of ionized vapor about auxiliary anodes associated with the main anodes of an electric current rectifier of the metallic vapor arcing type to secure harmless discharging of potential surges in the rectifying system.

Fig. 2 schematically illustrates an embodiment of the invention similar to that shown in Fig. 1 and operating similarly except that the current is supplied to the excitation anode from the direct current output circuit, and

Fig. 3 schematically illustrates an embodiment of the invention in which the excitation anode is omitted and the discharge anodes are so arranged as to maintain a zone of highly ionized vapor about all of the auxiliary anodes thus facilitating discharging of surges by way of the auxiliary anodes.

Referring more particularly to the drawing by characters of reference, the reference numeral 6 designates an alternating current transmission line from a suitable source of supply (not shown) and connected to supply the primary winding 7 of a transformer of which the different phases of the star connected secondary winding 8 are each connected through a reactance 9 of low value with a main anode 10 of an electric current rectifier having a casing 11 enclosing the anodes and retaining a cathode 12 of vaporizable material therein. The anodes 10 extend into the casing 11 in insulated relation and are partially enclosed within are guides 13 and the portion of the casing 11 retaining the cathode 13 is likewise insulated from the remaining portions of the casing structure. A direct current output circuit is formed by a conductor 16 connected with the neutral point of the transformer secondary winding 8, a conductor 17 connected with the cathode 12 and a load herein represented by a resistance 18 supplied from the conductors 16 and 18. The anodes 10 are supplied with alternating current from the transformer 7, 8, as is usual in electric current rectifying systems and the rectified direct current is supplied to the load 18.

Each of the main anodes 10 has associated therewith an auxiliary electrode 21 connected with the same phase of the transformer secondary winding 8 through an ohmic resistance 22. The auxiliary electrodes 21 are insulated from the rectifier casing 11 and extend into the rectifier into a zone of highly ionized va or. An auxiliar electrode 26 is tween the electrode 26 and the cathode 12 thus maintaining the vapor about the electrodes 21 and 26 highly ionized. Such arc impinging electrodes 21 excites and maintains the discharge path including such electrodes in a highly conductive condition thus causing surges to discharge through resistances 22 and auxiliary anodes 21 rather than through the reactances 9 and the main anodes 10. It will be understood that, although only one excitation anode 26 has been shown, a plurality of such excitation anodes may be used and may be grouped about the discharge anodes 21 to secure more extensive contact of the exciting arc with the discharge anodes 21.

The anodes usually present in an electric current rectifier of the metallic vapor type for the purpose of maintaining the are which is to be picked up by the main anodes, frequently referred to as the are maintaining anodes, maintain such are continuously as long as current is supplied and therefore maintain a portion of the vapor within the rectifier in highly ionized condition. Proper location of the discharge anodes relative to the are maintaining anodes therefore allows such anodes to be used for the purpose for which the anode 26 is used in Fig. 1.

The embodiment shown in Fig. 2 differs from that shown in Fig. 1 only in the connection of the excitation anode 26. Thus anode 26 is adjustably connected with a resistance 31 connected across the direct current bus bars 16 and 17 in parallel with the load 18. Operation of the present embodiment is prob ably due to the fact that the excitation anode is continuously energized, when the rectifier is in operation, by the direct current produced by the rectifier and the action of such anode thus maintains the vapor about the discharge anodes in highly ionized condition. The potential which is required to cause a flashover between the discharge anodes and the excitation anode is thus less than the potential required to cause flashover to the main anodes. Surges therefore discharge from the anodes 21 to the anode 26 rather than from the main anodes 10.

Fig. 3 represents an embodiment of the invention in which the excitation anodes 26 shown in F 1 and 2 are omitted, the discharge anodes 21 connected with each phase of the transformer secondary winding 8 of the supply transformer through resistance 22 being arranged to maintain the vapor 'ithin zone about the discharge anodes in highly ionized condition. For this reason, the discharge anodes 21 are preferably arranged closely adjacent to each other. As is well known, current is carried in a rectifier of the metallic vapor arcing type by the main anode having the highest potential above cathode potential at any given moment. The discharge anode associated with the anode in operation is then also at a potential above cathode potential and carries a certain amount of current in parallel with the main anode and all discharge anodes carry current in the same sequence as the current is carried by the associated main anodes thus automatically maintaining the vapor about the discharge anodes in a highly ionized condition. Upon the occurrence of a surge in any one of the transformer secondary winding phases, such surge will therefore be discharged from the discharging anode connected with such phase to the cathode and the surge potential will be dissipated in the resistances 22 Without effecting the operation of the main anodes 10.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In an electric current rectifying system, an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, anodes extending into the casing and subject to impression of potential surges thereon, and means associated with the anodes to discharge the surges therefrom, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, and means for maintaining the first said means in condition to discharge the surges more readily than through the anodes.

2. In an electric current rectifying system,

an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, main anodes and discharge anodes extending into the casing and subject to impression of potential surges thereon, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, and means for maintaining a highly ionized vapor filled zone about the discharge anodes to cause discharge of the surges by way of the discharge anodes.

3. In an electric current rectifying system, an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, main anodes and discharge anodes extending into the casing and subject to the impression of potential surges thereon, each of the main anodes being connected with one of the discharge anodes, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, and means for maintaining a highly ionized vapor filled zone about the discharge anodes to cause discharge of surges by way of the discharge anodes.

4. In an electric current rectifying system, an alternating'current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the easing, main anodes and discharge anodes ex tending into the casing and subject to potential surges, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, an excitation anode arranged within the casing for maintaining'a highly ionized vapor filled zone about the discharge anodes to cause discharge of surges by way of the discharge anodes, and means for impressing a potential on the said excitation anode to maintain the same in excited condition.

5. In an electric current rectifying system, an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, main anodes and discharge anodes extending into the casing and subject to potential surges, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, an excitation anode arranged within the easing for maintaining a highly ionized vapor filled zone about the discharge anodes to cause discharge of surges by the discharge anodes, the discharge anodes and the excitation anode being arranged in closely adjacent relation, and means for impressing a potential on the last said anode to maintain the same in excited condition.

6. In an electric current rectifying system, an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, main anodes and discharge anodes extending into the casing and subject to potential surges, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, an excitation anode arranged within said casing for maintaining a highly ionized vapor filled zone about the discharge anodes to cause discharge of surges by the discharge anodes, and a source of potential other than said alternating current supply line and said direct current line for impressing a potential on the said excitation anode to maintain the same in excited condition.

7; In an electric current rectifying system, an alternating current supply line, an electric current rectifier of the metallic vapor arcing type comprising a casing, a cathode of vaporizable material retained within the casing, main anodes and discharge anodes extending into the casing and subject to potential surges, a transformer connecting said supply line and the anodes, a direct current line supplied by said rectifier, an excitation anode arranged Within the casing for maintaining a highly ionized vapor filled zone about the discharge anodes to cause discharge of surges by the discharge anodes, and a resistance connected across said direct current line, the last said excitation anode being adjnstably connected with said resistance to impress a potential on said anode to maintain the same in excited condition.

In testimony whereof, the signature of the inventor is aifixed hereto.

ERNST KOBEL. 

